Composite attachment structure with 3D weave

ABSTRACT

An attachment structure for a case includes a V-groove defined by first and second arms extending circumferentially around the case and meeting at a lower portion. At least a portion of the attachment structure is a three-dimensionally woven composite.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from U.S. PCT Application No.PCT/US14/14766, filed Feb. 5, 2014 for “COMPOSITE ATTACHMENT STRUCTUREWITH 3D WEAVE” by Christopher M. Quinn and Sreenivasa R. Voleti, andfrom U.S. Provisional Application No. 61/766,388, filed Feb. 19, 2013for “COMPOSITE ATTACHMENT STRUCTURE WITH 3D WEAVE” by Christopher M.Quinn and Sreenivasa R. Voleti.

BACKGROUND

Composite materials offer potential design improvements in gas turbineengines. For example, in recent years composite materials have beenreplacing metals in gas turbine engine components because of their highstrength and low weight. Typical composite components can be formed of aplurality of two-dimensional filament reinforced plies or laminationsstacked on each other. These can be cut and stacked in a mold. The moldcan then be injected with a resin and cured. The strength of the pliesis high in the plane of the plies and lowest normal to the plane,through the thickness.

SUMMARY

An attachment structure for a case includes a V-groove defined by firstand second arms extending circumferentially around the case and meetingat a lower portion. At least a portion of the attachment structure is athree-dimensionally woven composite.

A method of forming a V-groove for a case includes three-dimensionallyweaving at least a portion of an attachment structure; and connectingthe attachment structure circumferentially around an end of the fancase.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates an example gas turbine engine thatincludes a fan section, a compressor section, a combustor section and aturbine section.

FIG. 2A is a perspective view of a Fan Case with a V-groove.

FIG. 2B is a cross-sectional view of the V-groove of FIG. 2A.

FIG. 3A is an enlarged cross-sectional view of an angle to angleinterlock three-dimensional weave pattern for a V-groove.

FIG. 3B is an enlarged cross-sectional view of a through-thicknessthree-dimensional weave pattern for a V-groove.

DETAILED DESCRIPTION

FIG. 1 schematically illustrates an example gas turbine engine 20 thatincludes fan section 22, compressor section 24, combustor section 26 andturbine section 28. Alternative engines might include an augmentersection (not shown) among other systems or features. Fan section 22drives air along bypass flow path B while compressor section 24 drawsair in along core flow path C where air is compressed and communicatedto combustor section 26. In combustor section 26, air is mixed with fueland ignited to generate a high pressure exhaust gas stream that expandsthrough turbine section 28 where energy is extracted and utilized todrive fan section 22 and compressor section 24.

Although the disclosed non-limiting embodiment depicts a turbofan gasturbine engine, it should be understood that the concepts describedherein are not limited to use with turbofans as the teachings may beapplied to other types of turbine engines; for example a turbine engineincluding a three-spool architecture in which three spoolsconcentrically rotate about a common axis and where a low spool enablesa low pressure turbine to drive a fan via a gearbox, an intermediatespool that enables an intermediate pressure turbine to drive a firstcompressor of the compressor section, and a high spool that enables ahigh pressure turbine to drive a high pressure compressor of thecompressor section.

The example engine 20 generally includes low speed spool 30 and highspeed spool 32 mounted for rotation about an engine central longitudinalaxis A relative to an engine static structure 36 via several bearingsystems 38. It should be understood that various bearing systems 38 atvarious locations may alternatively or additionally be provided.

Low speed spool 30 generally includes inner shaft 40 that connects fan42 and low pressure (or first) compressor section 44 to low pressure (orfirst) turbine section 46. Inner shaft 40 drives fan 42 through a speedchange device, such as geared architecture 48, to drive fan 42 at alower speed than low speed spool 30. High-speed spool 32 includes outershaft 50 that interconnects high pressure (or second) compressor section52 and high pressure (or second) turbine section 54. Inner shaft 40 andouter shaft 50 are concentric and rotate via bearing systems 38 aboutengine central longitudinal axis A.

Combustor 56 is arranged between high pressure compressor 52 and highpressure turbine 54. In one example, high pressure turbine 54 includesat least two stages to provide a double stage high pressure turbine 54.In another example, high pressure turbine 54 includes only a singlestage. As used herein, a “high pressure” compressor or turbineexperiences a higher pressure than a corresponding “low pressure”compressor or turbine.

The example low pressure turbine 46 has a pressure ratio that is greaterthan about 5. The pressure ratio of the example low pressure turbine 46is measured prior to an inlet of low pressure turbine 46 as related tothe pressure measured at the outlet of low pressure turbine 46 prior toan exhaust nozzle.

Mid-turbine frame 58 of engine static structure 36 is arranged generallybetween high pressure turbine 54 and low pressure turbine 46.Mid-turbine frame 58 further supports bearing systems 38 in turbinesection 28 as well as setting airflow entering low pressure turbine 46.

The core airflow C is compressed by low pressure compressor 44 and thenby high pressure compressor 52, mixed with fuel and ignited in combustor56 to produce high speed exhaust gases, and then expanded through highpressure turbine 54 and low pressure turbine 46. Mid-turbine frame 58includes vanes 60, which are in the core airflow path and function as aninlet guide vane for low pressure turbine 46. Utilizing vane 60 ofmid-turbine frame 58 as the inlet guide vane for low pressure turbine 46decreases the length of low pressure turbine 46 without increasing theaxial length of mid-turbine frame 58. Reducing or eliminating the numberof vanes in low pressure turbine 46 shortens the axial length of turbinesection 28. Thus, the compactness of gas turbine engine 20 is increasedand a higher power density may be achieved.

The disclosed gas turbine engine 20 in one example is a high-bypassgeared aircraft engine. In a further example, gas turbine engine 20includes a bypass ratio greater than about six (6), with an exampleembodiment being greater than about ten (10). The example gearedarchitecture 48 is an epicyclical gear train, such as a planetary gearsystem, star gear system or other known gear system, with a gearreduction ratio of greater than about 2.3.

In one disclosed embodiment, gas turbine engine 20 includes a bypassratio greater than about ten (10:1) and the fan diameter issignificantly larger than an outer diameter of low pressure compressor44. It should be understood, however, that the above parameters are onlyexemplary of one embodiment of a gas turbine engine including a gearedarchitecture and that the present disclosure is applicable to other gasturbine engines.

A significant amount of thrust is provided by bypass flow B due to thehigh bypass ratio. Fan section 22 of engine 20 is designed for aparticular flight condition—typically cruise at about 0.8 Mach and about35,000 feet. The flight condition of 0.8 Mach and 35,000 ft., with theengine at its best fuel consumption—also known as “bucket cruise ThrustSpecific Fuel Consumption (‘TSFC’)”—is the industry standard parameterof pound-mass (lbm) of fuel per hour being burned divided by pound-force(lbf) of thrust the engine produces at that minimum point.

“Low fan pressure ratio” is the pressure ratio across the fan bladealone, without a Fan Exit Guide Vane (“FEGV”) system. The low fanpressure ratio as disclosed herein according to one non-limitingembodiment is less than about 1.50. In another non-limiting embodimentthe low fan pressure ratio is less than about 1.45.

“Low corrected fan tip speed” is the actual fan tip speed in ft/secdivided by an industry standard temperature correction of [(Tram °R)/518.7° R]^(0.5). The “Low corrected fan tip speed”, as disclosedherein according to one non-limiting embodiment, is less than about 1150ft/second.

The example gas turbine engine includes fan 42 that comprises in onenon-limiting embodiment less than about twenty-six fan blades and fancase 43 with V-groove 60 surrounding fan 42. In another non-limitingembodiment, fan section 22 includes less than about twenty fan blades.Moreover, in one disclosed embodiment low pressure turbine 46 includesno more than about six turbine rotors schematically indicated at 34. Inanother non-limiting example embodiment low pressure turbine 46 includesabout three turbine rotors. A ratio between number of fan blades 42 andthe number of low pressure turbine rotors is between about 3.3 and about8.6. The example low pressure turbine 46 provides the driving power torotate fan section 22 and therefore the relationship between the numberof turbine rotors 34 in low pressure turbine 46 and number of blades 42in fan section 22 disclose an example gas turbine engine 20 withincreased power transfer efficiency.

In a turbofan engine, lighter components generally lead to moreefficient performance. If less energy is expended moving internal engineparts, more energy is available for useful work. At the same time, thecomponents themselves must be strong enough to withstand forces typicalfor the operating environment and performance envelope. Safetyconsiderations based on the frequency and/or severity of possiblefailure will often dictate that the engine components also be able towithstand certain atypical, yet foreseeable events as well. Becausestronger components are often heavier and/or more expensive, a balancemust be struck between efficiency, safety, and cost.

Few locations in an aircraft are more representative of efforts tooptimize the balance between efficiency, safety, and cost than engine20. While lighter materials are preferable to improve efficiency, thehigh risk of severe consequences from engine damage will require thatengine 20 be made of components having additional margins of safety.Fiber composites typically have low weight, and three-dimensionalweaving of the composites can greatly increase strength in the thicknessdirection.

FIG. 2A is a perspective view of fan case 43 with attachment structure60, and FIG. 2B is a cross-sectional view of attachment structure 60.FIGS. 2A-2B include fan case 43 with forward end 62 and aft end 64; andattachment structure 60, which includes connection ring 66 and V-groove68 defined by arms 70, 72 and lower portion 74.

Connection ring 68 is connected to aft end 64 of fan case 43 with bolts75. In alternative embodiments, attachment structure 60 can be formedintegral to fan case 43 (see FIG. 1) and no fasteners are needed.

Attachment structure 60 is formed of composite materials, with at leastportion formed of a three-dimensional weave. In the embodiment shown,lower portion 74 is a three-dimensional weave with arms 70, 72 andconnection ring 68 formed of two-dimensional weaves. The two-dimensionalweaves can be a plurality of stacked two-dimensional plies or fabricskins with elongated fibers extending through the plies at specifiedorientations. These can be stacked adjacent the three-dimensional weaveportion 74 in a mold, injected with resin and then cured. Otherembodiments could use preimpregnated composites, and/or could be formedwith different methods. In other embodiments, three-dimensional weaveextends into arm 70, arm 72, connection ring 68 and/or fan case 43.

When in engine 20, V-groove 68 is used to connect fan case 43 to otherengine components, for example a thrust reverser. This connection putsforce on arm 72 of attachment structure 60, as indicated by force arrowsF, resulting in high axial forces in V-groove 68. In the past, V-grooveswere made of high-strength metal to resist these forces. To reduceweight, composites can be used to form V-groove 60, replacing theheavier metal.

As V-groove 68 must withstand high axial loads, a typicaltwo-dimensional composite could be subject to delamination, particularlyin lower portion 74 of attachment structure 60. V-groove 68 includes athree-dimensional weave in lower portion 74 of attachment structure 60to resist the high axial loads, increasing stiffness and strength in thethickness direction, thereby preventing delamination. By including athree-dimensional weave in parts of attachment structure 60, attachmentstructure can be made of light-weight materials while maintaining therequired strength for connection to other engine components. Athree-dimensional weave in certain parts of attachment structure 60 canalso make the entire attachment structure 60 more resistant to damageand fatigue by increasing strength and inhibiting damage propagation.

FIG. 3A is an enlarged cross-sectional view at 3-3 of FIG. 2B, showingone plane of an angle to angle interlock three-dimensional weave patternin attachment structure 60, and include tow yarns 78 (“tows”) and warpyarns 80.

The yarns of attachment structure 60 are formed from bundles of fibers.Example fibers for the yarns of attachment structure 60 include but arenot limited to graphite fibers, glass fibers, silicon carbide fibers andboron fibers and combinations thereof. Example resins for curing includebut are not limited to epoxy resins and epoxy resins containingadditives such as rubber particulates.

In the three-dimensional weave of FIG. 3A, warp yarns 80 intersect withother yarns (fill yarns (81), not shown in FIG. 3A, but shown in theembodiment of FIG. 3B) to form two-dimensional woven plies. Warp andfill yarns may be oriented at any in-plane angle. Tows 78 a-78 d(referred to collectively as tows or tow yarns 78) extend in thethickness direction of weave to interlock warp yarns 80 in anangle-to-angle interlock weave pattern. In the pattern shown, tow yarns78 interlock with every second warp yarn 80. For example, tow 78 a iswoven from the top of the first warp yarn 80 from the top of column C4to under the second warp yarn 80 in column C6 to over the first warpyarn 80 in column C8 over the length of five columns.

Because tow yarns 78 weave, they have crimp angles α and are notstraight. Crimp angles α create chordwise undulations in tow yarns 78and decrease the stiffness properties in that direction. The magnitudeof crimp angle α affects the stiffness and strength properties in boththe inplane and through-thickness directions. For example, a largercrimp angle results in a larger decrease in inplane strength andstiffness properties in that direction but provides a larger increase inthrough-thickness stiffness and strength properties.

Tow yarns 78 undulate over and under at least one layer of warp yarns 80to hold adjacent two-dimensional weaves together, giving woven section74 strength in the thickness direction. Tow yarns 78 do not go all theway through the thickness in an angle-to-angle interlock weave, insteadgradually weaving layers together to form entire three-dimensionalweave.

FIG. 3B is an enlarged cross-sectional view at 3-3 of FIG. 2B, showing athrough-thickness three-dimensional weave pattern for an attachmentstructure 60, and include tows 78 a-78 f (collectively referred to astows 78 or tow yarns 78) and warp yarns 80. As with FIG. 3A, tows 78extend in the thickness direction and warp yarns 80 intersect with fillyarns (81) to form two-dimensional woven plies.

In a through-thickness weave pattern, as shown in FIG. 3B, tow yarns 78extend the entire thickness of three-dimensional woven part 74,interlocking with the upper most and lower most warp yarns 80.

By including a three-dimensional weave in at least a portion ofattachment structure 60, attachment structure 60 can be made oflight-weight composite materials and still have the require strength towithstand through the thickness forces F in V-groove 68 when connectingfan case 43 to other engine components. Three-dimensionally wovenportion of attachment structure 60 can help attachment structure 60resist delamination that these forces F can cause in traditionaltwo-dimensional woven composites by increasing interlaminar strength andstiffness.

While discussed as tow yarns 78 weaving together two-dimensional plies,in alternative embodiments, attachment structure 60 three-dimensionalweave portion can be integrally woven as a single three-dimensionalpiece. Additionally, weave patterns shown in FIGS. 3A-3B are for examplepurposes only and can be varied depending on engine requirements.

An attachment structure for a fan case includes a V-groove defined byfirst and second arms extending circumferentially around the fan caseand meeting at a lower portion, wherein at least a portion of theattachment structure is a three-dimensionally (3D) woven composite.

Additional and/or alternative embodiments include the lower portion ofbeing made of the three-dimensionally woven composite; at least one ofthe arms being also made of the three-dimensionally woven composite; aconnection portion extending outwards from the V-groove to connect tothe fan case; the connection portion being integral to the fan case; theconnection portion being a three-dimensionally woven composite; thethree-dimensionally woven composite comprising an angle-to-angleinterlock weave pattern; the three-dimensionally woven compositecomprising a through-thickness weave pattern; and/or the entireattachment structure being a three-dimensionally woven composite.

A fan case includes a cylindrical portion with a first end and a secondend; and an attachment structure on the second end with at least aportion comprising a three-dimensionally woven composite.

Additional and/or alternative embodiments include the attachmentstructure extending circumferentially radially outward around the secondend; the attachment structure being shaped to connect the fan case toanother engine component; the attachment structure having a V-grooveshaped cross-section defined by first and second arms joined at a lowerportion; the lower portion being a three-dimensionally woven composite;at least one of the first and second arms being a three-dimensionallywoven composite; the attachment structure being connected to thecylindrical portion with fasteners; and/or the attachment structurebeing formed integral to the cylindrical portion.

A method of forming an attachment structure for a fan case includesthree-dimensionally weaving at least a portion of an attachmentstructure; and connecting the attachment structure circumferentiallyaround an end of the fan case.

Additional and/or alternative embodiments include the step ofthree-dimensionally weaving at least a portion of an attachmentstructure comprising through-thickness weaving at least a portion of theattachment structure; and/or the step of three-dimensionally weaving atleast a portion of an attachment structure comprising angle-to-angleinterlock weaving at least a portion of the attachment structure.

While the invention has been described with reference to an exemplaryembodiment(s), it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment(s) disclosed, but that theinvention will include all embodiments falling within the scope of theappended claims.

The invention claimed is:
 1. An attachment structure for an end of a fancase of an engine, the attachment structure comprising: a V-groove,configured to connect the fan case to other engine components, definedby first and second arms extending circumferentially around the case andmeeting at a lower portion, wherein the first and second arms extendradially outward from the lower portion and the case, wherein at least aportion of the attachment structure is a three-dimensionally (3D) wovencomposite, and wherein the V-groove includes a three-dimensional weavein the lower portion of the attachment structure, wherein the weavecomprises: warp yarns intersecting with fill yarns to formtwo-dimensional woven plies; and tows yarns extending in a thicknessdirection of the weave to interlock the warp yarns in an angle-to-angleinterlock weave pattern, and wherein the tow yarns extend the entirethickness of the lower portion, interlocking with the upper most andlower most warp yarns.
 2. The attachment structure of claim 1, whereinat least one of the arms is also made of the three-dimensionally wovencomposite.
 3. The attachment structure of claim 2, and furthercomprising a connection portion extending outwards from the V-groove toconnect to the case.
 4. The attachment structure of claim 3, wherein theconnection portion is a three-dimensionally woven composite.
 5. Theattachment structure of claim 1, wherein the entire attachment structureis a three-dimensionally woven composite.
 6. A fan case of an engine,the fan case comprising: a cylindrical portion with a first end and asecond end; and an attachment structure on the second end with at leasta portion comprising a three-dimensionally woven composite, theattachment structure being configured to connect the fan case to otherengine components, wherein the attachment structure has a V-grooveshaped cross-section defined by first and second arms joined at a lowerportion, wherein the first and second arms extend radially outward fromboth the lower portion and the second end.
 7. The case of claim 6,wherein the attachment structure extends circumferentially around thesecond end.
 8. The case of claim 6, wherein the lower portion is athree-dimensionally woven composite.
 9. The case of claim 6, wherein atleast one of the first and second arms is a three-dimensionally wovencomposite.
 10. The case of claim 6, wherein the case is a fan case. 11.A method of forming an attachment structure for connecting a fan case tocomponents of an engine, the method comprising: three-dimensionallyweaving a lower portion of a V-groove of the attachment structure,wherein the weaving comprises: intersecting warp yarns with fill yarnsto form two-dimensional woven plies; and extending tow yarns in anangle-to-angle interlock weave pattern, wherein the tow yarns interlockwith every second warp yarn; and connecting the attachment structurecircumferentially around an end of the case such that a first arm and asecond arm of the V-groove extend radially outward from both the lowerportion and the end of the case.
 12. The method of claim 11, wherein thestep of three-dimensionally weaving the lower portion of the V-groovecomprises: through-thickness weaving at least a portion of theattachment structure.